Semiconductor device with PMOS and NMOS transistors

ABSTRACT

A semiconductor device including an NMOS region and a PMOS region in the same substrate, wherein the semiconductor device includes a strained Si layer which is provided on the substrate in the NMOS region and in which the surface has a plane orientation different from that of the substrate, and a strained SiGe layer which is provided on the substrate in the PMOS region and which is composed of a stained layer having the same plane orientation as that of the surface of the substrate; and a method of manufacturing the same.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device and a method ofmanufacturing a semiconductor device, particularly to a semiconductordevice including a CMOS transistor (CMOS) in which a channel layerincludes a strained layer and a method of manufacturing the same.

In semiconductor devices, particularly CMOS devices, there have beenconducted enhancement of drive capability and reduction in powerconsumption from the viewpoint of enhancing the performance of thedevices, and these developments have been made by thinning the gateinsulation film and miniaturizing the gate structure. However, due tothe conspicuous tendencies toward an increased leak current, a shortchannel effect and the like; it has been becoming difficult to enhancethe drive capability by simple miniaturization.

In view of this, in recent years, for enhancing the device performance,a trial to utilize a heterostructure of silicon (Si) andsilicon-germanium (SiGe) has been made. For example, it is known thatwhen, to enhance the speed of an NMOS transistor (NMOS), a mixed crystallayer of Si and germanium (Ge) larger in lattice constant than Si isgrown on an Si substrate, thereby forming a relaxed SiGe layer in alattice relaxed state, then a strained Si layer in a tension-strainedstate is formed thereon, and a channel region is formed in the strainedSi layer, the carrier mobility (electron mobility) in the channel regionis enhanced. It is also known that when, in order for example to enhancethe speed of a PMOS transistor (PMOS), a strained SiGe layer in acompression-strained state is formed on an Si substrate, and a channelregion is formed in the strained SiGe layer, the carrier mobility (holemobility) in the channel region is enhanced.

Based on the above, an example of CMOS device has been reported in whicha strained Si layer is used as the NMOS channel region and a strainedSiGe layer is used as the PMOS channel region. Such a CMOS device hasbeen manufactured by a method in which a relaxed SiGe layer, a strainedSi layer and a strained SiGe layer are laminatingly formed on an Sisubstrate, the strained SiGe layer is removed and the strained Si layeris removed to a certain level of depth in the NMOS region, therebyexposing the strained Si layer having a high coefficient of straining,then the channel region of the NMOS transistor is formed in the strainedSi layer thus exposed, and the channel region of the PMOS transistor isformed in the strained SiGe layer, to manufacture the CMOS device (see,for example, Japanese Patent Laid-open No. Hei 10-93025).

On the other hand, it has been reported that in NMOS, the electronmobility is higher in the order (100)>(111)>(110) in terms of the planeorientation of the surface of the Si substrate, whereas in PMOS, thehole mobility is higher in the order of (110)>(111)>(100) in terms ofthe plane orientation of the surface of the Si substrate (See M. Yang etal, “IEEE Electron Device Letters” (USA), 2003, Vol. 24, p. 339, forexample).

SUMMARY OF THE INVENTION

However, sufficient carrier mobility cannot be obtained even with theabove-mentioned CMOS device in which the strained Si layer is used forthe NMOS channel region and the strained SiGe layer is used for the PMOSchannel region. In addition, in the above-mentioned method ofmanufacturing a CMOS device, the strained SiGe layer and the strained Silayer to a certain level of thickness are removed so as to expose thestrained Si layer, on the NMOS region side, so that a step is generatedbetween the NMOS region and the PMOS region. Therefore, even in the casewhere gate electrodes in the regions are formed and then an insulationfilm is formed in the state of covering the gate electrodes to achieveleveling, the step is liable to be left, and the leveling property ofthe insulation film tends to be worsened. As a result, the processmargin at the time of light exposure or etching for forming contactholes thereafter would be small, and the contact holes would not beformed with high accuracy.

Furthermore, in an Si substrate of which the surface has a planeorientation of (100) and which is used ordinarily, the hole mobilityobtained in PMOS is not sufficient, although the electron mobility inNMOS is high.

In order to solve the above-mentioned problems, according to the presentinvention, there is provided a semiconductor device including a firstdevice region and a second device region in the same substrate, whereinthe semiconductor device includes: a first semiconductor layer providedon the substrate in the first device region and having a planeorientation different from that of the surface of the substrate; and asecond semiconductor layer provided on the substrate in the secondsemiconductor region and including a strained layer having the sameplane orientation with that of the surface of the substrate.

According to such a semiconductor device, there are provided the firstsemiconductor layer provided on the substrate in the first device regionand having a plane orientation different from that of the surface of thesubstrate, and the second semiconductor layer provided on the substratein the second device region and having the same plane orientation withthat of the surface of the substrate. This makes it possible to providethe first semiconductor layer and the second semiconductor layer withrespective plane orientations optimum for enhancing the carriermobility, in both the first device region and the second device region.In addition, since the second semiconductor layer includes a strainedlayer, the carrier mobility in the second semiconductor layer can befurther enhanced. Where the first semiconductor layer is also comprisedof a strained layer, the carrier mobilities in both the first deviceregion and the second device region can be further enhanced.

In addition, according to the present invention, there is provided amethod of manufacturing a semiconductor device including a first deviceregion and a second device region in the same substrate, wherein thefollowing steps are sequentially carried out. In a first step, aninsulation layer is formed on the substrate, and a first semiconductorlayer having a plane orientation different from that of the surface ofthe substrate is laminated on the insulation layer. Next, in a secondstep, the insulation layer and the first semiconductor layer are removedto expose the substrate in the second device region. Subsequently, in athird step, a second semiconductor layer including a strained layer isepitaxially grown on the exposed substrate in the second device regionin the condition of maintaining the plane orientation of the surface ofthe substrate.

According to such a method of manufacturing a semiconductor device, thefirst semiconductor layer having a plane orientation different from thatof the surface of the substrate is formed on the substrate in the firstdevice region, so that the first semiconductor layer and the secondsemiconductor layer different in plane orientation are formedrespectively in the first device region and the second device regionwhich are provided in the same substrate. This ensures that the firstsemiconductor layer and the second semiconductor layer are formed withrespective plane orientations optimum for enhancing the carriermobilities, whereby the carrier mobilities in the first device regionand the second device region can be enhanced. In addition, the secondsemiconductor layer is composed of a strained layer, whereby the carriermobility in the first device region can be further enhanced. Where thefirst semiconductor layer is also composed of a strained layer, thecarrier mobilities in both the first device region and the second deviceregion can be further enhanced. Besides, since the second semiconductorlayer is grown on the substrate having been deprived of the insulationlayer and the first semiconductor layer in the second device region, thegeneration of a step between the first device region and the seconddevice region is restrained.

As has been described above, according to the semiconductor device andthe method of manufacturing the same of the present invention, thecarrier mobilities in the first device region and the second deviceregion which are provided in the same substrate can be enhanced. As aresult, in the case where the first device region is one of an NMOSregion and a PMOS region in a CMOS device and the second device regionis the other of the NMOS region and the PMOS region, the carriermobility can be enhanced in both the NMOS region and the PMOS region, sothat the CMOS device performance can be enhanced. In addition, since thegeneration of a step between the NMOS region and the PMOS region isrestrained, contact holes for connection to a transistor formed in eachof the regions can be formed with high accuracy, and he yield can beenhanced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional configurational diagram for illustrating a firstembodiment of the semiconductor device according to the presentinvention;

FIGS. 2A to 2L are manufacturing step sectional diagrams forillustrating a first embodiment of the method of manufacturing asemiconductor device according to the present invention;

FIG. 3 is a sectional configurational diagram for illustrating a secondembodiment of the semiconductor device according to the presentinvention; and

FIGS. 4A to 4L are manufacturing step sectional diagrams forillustrating the second embodiment of the method of manufacturing asemiconductor device according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, embodiments of the present invention will be described in detailbelow, based on the drawings.

First Embodiment

FIG. 1 is a sectional configurational diagram of a CMOS device accordingto this embodiment. As shown in the figure, a p-type Si substrate(substrate 11) composed of an Si single crystal layer whose surface hasa plane orientation of (110) is provided therein with an NMOS region(first device region) A and a PMOS region (second device region) B. Onthe substrate 11 is provided a relaxed SiGe layer 12 in the state ofmaintaining the plane orientation (110) of the surface of the substrate11. Though not shown in the figure, the relaxed SiGe layer 12 iscomposed, for example, of an inclined SiGe layer containing Ge mixed inan Si layer so that the Ge compositional ratio in the Si layer graduallyincreases from 0 to x along the upward direction, and an Si_(1-x)Ge_(x)layer which is provided on the inclined SiGe layer and in which the Gecompositional ratio in the Si layer is x.

In addition, an insulation layer 13 formed of silicon oxide (SiO₂) isprovided on the relaxed SiGe layer 12 in the NMOS region A, and astrained Si layer 21 composed of a strained layer in a tension-strainedstate is provided on the insulation layer 13. The strained Si layer 21is formed to have a plane orientation (100) which is different from theplane orientation (110) of the substrate 11 and which promises a higherelectron mobility as compared with other plane orientations.Incidentally, while the strained Si layer 21 in the tension-strainedstate is used here, the layer is not particularly limited and may be anystrained layer in the tension-strained state in as much as the layer canenhance the electron mobility.

As will be detained later in connection with a manufacturing method, thestrained layer 21 is formed from, and in the state of maintaining theplane orientation of, a p-type Si substrate (joined substrate) composedof an Si single crystal layer whose surface has a plane orientation of(100), different from that of the first substrate 11. The NMOS region Ais in the state of having an SOI (Silicon On Insulator) structure,specifically, an SSOI (Strained-Silicon On Insulator) structure formedby laminating the strained Si layer 21 on the insulation layer 13.

On the other hand, a strained SiGe layer 31 composed of a strained layerin a compression-strained state which is composed of an Si_(1-y)Ge_(y)layer (x<y) having a Ge compositional ratio higher than that of theSi_(1-x)Ge_(x) layer of the relaxed SiGe layer 12, for example, isprovided on the relaxes SiGe layer 12 in the PMOS region B. The strainedSiGe layer 31, by being in the compression-strained layer, is soconfigured as to be higher in hole mobility than a non-strained Silayer. In addition, the strained SiGe layer 31 is formed by epitaxialgrowth in the state of maintaining the plane orientation of the relaxedSiGe layer 12, i.e., in the state of maintaining the plane orientation(110) of the surface of the substrate 11, whereby it is provided with aplane orientation (110) which promises a higher hole mobility ascompared with other plane orientations. Incidentally, while the strainedSiGe layer 31 in the compression-strained state is used here, the layeris not particularly limited and may be any strained layer in thecompression-strained state inasmuch as the layer can enhance the holemobility.

Here, since the coefficient of straining of the strained SiGe layer 31is determined by the compositional ratio of Si and Ge in theSi_(1-x)Ge_(x) layer of the relaxed SiGe layer and the compositionalratio of Si and Ge in the strained SiGe layer 31, the compositionalratios in the Si_(1-x)Ge_(x) layer of the relaxed SiGe layer 12 and inthe Si_(1-y)Ge_(y) layer of the strained SiGe layer 31 are controlled soas to provide the strained SiGe layer 31 with a coefficient of strainingwhich is optimum for enhancing the hole mobility.

In addition, a thin film form cap film 32 formed of Si, for example, isprovided on the strained SiGe layer 31. The cap film 32 is necessary forenhancing the interface condition between the strained SiGe layer 31 anda gate electrode 33 which will be described later, and the cap film 32is so configured that the surface side of the cap film 32 or the capfilm 32 itself becomes a gate insulation film by being subjected to athermal oxidizing treatment.

A trench 14 in the state of reaching the inside of the relaxed SiGelayer 12 is provided on the surface side in the portion between the NMOSregion A and the PMOS region B, and a device isolation film 15 formed ofSiO₂ is provided in the trench 14. An NMOS transistor 20 and a PMOStransistor 30 are provided respectively in the NMOS region A and thePMOS region B thus isolated by the device isolation film 15.

The NMOS transistor 20 has a gate electrode 22 provided on the upperside of the strained Si layer 21 with a gate insulation film (not shown)therebetween, and side walls 23 are provided on both sides of the gateelectrode 22. In addition, the strained Si layer 21 is provided, on bothsides of the gate electrode 22, with source/drain regions 25 with an LDDregion 24 therebetween. Besides, that region in the strained Si layer 21which is defined between the source/drain regions (N⁺ type diffusionregions) 25 with the LDD region 24 therebetween constitutes a channelregion 26. In addition, a silicide layer 27 is provided on the surfaceside of the gate electrode 22 and the source/drain regions 25.

On the other hand, the PMOS transistor 30 has a gate electrode 33provided on the upper side of the strained SiGe layer 31 with a gateinsulation film (cap film 32) therebeetween, and side walls 34 areprovided on both sides of the gate electrode 33. In addition, thestrained SiGe layer 31 is provided, on both sides of the gate electrode33, with source/drain regions (P⁺ type diffusion regions) 36 with an LDDregion 35 therebetween. Besides, that region in the strained SiGe layer31 which is defined between the source/drain regions 36 with the LDDregion 35 therebetween constitutes a channel region 37. In addition, asilicide layer 38 is provided on the surface side of the gate electrode33 and the source/drain regions 36.

Now, a method of manufacturing the above-described CMOS device isillustrated in manufacturing step sectional diagrams shown in FIGS. 2Ato 3.

As shown in FIG. 2A, for example, a substrate 11 composed of a p-type Sisubstrate obtained by growing an Si single crystal layer with a surfaceplane orientation of (110) is provided with an NMOS region (NMOS formingregion) A for forming an NMOS transistor in the subsequent step, andwith a PMOS region (PMOS forming region) B for forming a PMOStransistor. Here, the NMOS region A corresponds to the first deviceregion set forth in the claims, and the PMOS region B to the seconddevice region.

First, a relaxed SiGe layer 12 is epitaxially grown on the substrate 11in the state of maintaining the plane orientation (110) of the surface.In this case, an inclined SiGe layer with the compositional ratio of Siand Ge gradually increasing from 0 to x in the direction toward theupper layer is epitaxially grown, and thereafter an Si_(1-x)Ge_(x) layerwith the compositional ratio of Si and Ge being 1-x:x is epitaxiallygrown on the inclined SiGe layer, thereby forming the relaxed SiGe layer12 composed of the inclined SiGe layer and the Si_(1-x)Ge_(x) layer.

Here, the coefficient of straining of a strained SiGe layer formed onthe relaxed SiGe layer 12 in the PMOS region B in the subsequent step isdetermined by the compositional ratio of Si and Ge in the Si_(1-x)Ge_(x)layer of the relaxed SiGe layer 12 and the compositional ratio of Si andGe in the strained SiGe layer, and the strained SiGe layer is providedwith a channel region of a PMOS transistor; therefore, the compositionalratios in the relaxed SiGe layer 12 and the Si_(1-x)Ge_(x) layer are soset as to provide a coefficient of straining which is optimum forenhancing the hole mobility.

Next, an insulation layer 13 formed of SiO₂, for example, is formed onthe relaxed SiGe layer 12. Here, by regulating the film thickness of theinsulation layer 13, the height of the surface of the NMOS region Aprovided by forming the strained Si layer on the insulation layer 13 iscontrolled. This ensures that, in the latter step in which the strainedSi layer and the insulation layer 13 on the PMOS region B side areremoved to expose the relaxed SiGe layer 12 and then the strained SiGelayer is grown on the relaxed SiGe layer 12 to form a surface layer inthe PMOS region B, the surface heights of the NMOS region A and the PMOSregion B are controlled to be roughly equal to each other.

On the other hand, on a joined substrate 41 composed of a p-type Sisubstrate having a plane orientation different from the planeorientation (110) of the surface of the substrate 11, for example, asurface plane orientation of (100), a relaxed SiGe layer 42 isepitaxially grown in the state of maintaining the plane orientation(100). In this case, an inclined SiGe layer with a compositional ratioof Ge to Si gradually increasing from 0 to z in the direction toward theupper layer is epitaxially grown, and thereafter an Si_(1-z)Ge_(z) layerwith a compositional ratio of Si and Ge being 1-z:z is epitaxially grownon the inclined SiGe layer, thereby forming the relaxed SiGe layer 42composed of the relaxed SiGe layer and the Si_(1-z)Ge_(z) layer. Here,the coefficient of restraining of a strained Si layer to be formed onthe relaxed SiGe layer 42 in the subsequent step is determined by thecompositional ratio in the Si_(1-z)Ge_(z) layer. Then, the strained Silayer is provided with a channel region of an NMOS transistor;therefore, the compositional ratio of Si and Ge in the Si_(1-z)Ge_(z)layer is so set as to provide a coefficient of straining which isoptimum for enhancing the electron mobility.

Subsequently, a strained Si layer (first semiconductor layer) 21 in atension-strained state is formed on the relaxed SiGe layer 42. Here, theheight of the surface of the NMOS region A can be controlled also by thefilm thickness of the strained Si layer 21, and the film thickness ofthe strained Si layer 21 is determined, to a certain extent, accordingto the coefficient of straining; therefore, it is preferable to controlthe height of the surface of the NMOS region A by the film thickness ofthe insulation layer 13.

Next, the insulation layer 13 formation side of the substrate 11 and thestrained Si layer 21 formation side of the joined substrate 41 areopposed to each other, and the insulation layer 13 and the strained Silayer 21 are laminated on each other. As a result, the strained Si layer21 having the plane orientation (100), which is different from the planeorientation of the substrate 11, is formed on the substrate 11.

Subsequently, as shown in FIG. 2B, hydrogen is introduced into thejoined substrate 41 (see FIG. 2A) and the relaxed SiGe layer 42 (seeFIG. 2A), and the joined substrate 41 and the relaxed SiGe layer 42 areremoved by etching, whereby the substrate 11 is provided with an SOIstructure, specifically an SSOI structure, in which the strained Silayer 21 is provided on the insulation film 13.

Next, as shown in FIG. 2C, an SiO₂ film 16 is formed on the strained Silayer 21, and a silicon nitride (SiN) layer 17 is formed on the SiO₂film 16. Subsequently, as shown in FIG. 2D, a resist pattern R is formedin the condition where the SiN film 17 on the PMOS region B side isexposed. Next, as shown in FIG. 2E, etching is conducted using theresist pattern R (see FIG. 2D) as a mask, whereby the SiN film 17 andthe SiO₂ film 16 are removed. Thereafter, the resist pattern R isremoved.

Subsequently, as shown in FIG. 2F, etching is conducted using the SiNfilm 17 and the SiO₂ film 16 as a mask, to remove the strained Si layer21 and the insulation layer 13 on the PMOS region B side, therebyexposing the surface of the relaxed SiGe layer 12.

Next, as shown in FIG. 2G, a protective film 18 formed of SiN is formedon the relaxed SiGe layer 12 in the state of covering the SiN film 17,the SiO₂ film 16, the strained Si layer 21 and the insulation layer 13on the NMOS region A side. Thereafter, as shown in FIG. 2H, theprotective film 18 is etched back, whereby the protective film 18 in thestate of covering the side surfaces of the insulation layer 13, thestrained Si layer 21, the SiO₂ film 16 and the SiN film 17 is left, andthe surface of the relaxed SiGe layer 12 on the PMOS region B side isexposed. The protective film 18 is provided for preventing the SiGelayer from growing sideways from the strained Si layer 21 on the NMOSregion A side at the time of epitaxially growing the strained SiGe layerin a compressed state on the relaxed SiGe layer 12 on the PMOS region Bside in the subsequent step.

Subsequently, as shown in FIG. 2I, a strained SiGe layer (secondsemiconductor layer) 31 in a compression-strained state is epitaxiallygrown on the exposed relaxed SiGe layer 12 on the PMOS region B side.The strained SiGe layer 31 in the compression-strained state is formedof an Si_(1-y)Ge_(y) layer (x<y) having a Ge compositional ratio higherthan that of the Si_(1-x)Ge_(x) layer on the upper layer side whichconstitutes the relaxed SiGe layer 12. The strained SiGe layer 31 is tobe provided with a channel region of a PMOS transistor in the subsequentstep, and, therefore, the compositional ratio of Si and Ge in theSi_(1-y)Ge_(y) layer is so set as to provide a coefficient of strainingwhich is optimum for enhancing the hole mobility. In this case, besides,it is preferable to grow the strained SiGe layer 31 to a height roughlythe same as that of the strained Si layer 21 on the NMOS region A side,and it is more preferable to grow the strained SiGe layer 31 to a heightobtained by subtracting the film thickness of a cap film to be formed onthe strained SiGe layer 31 in the subsequent step from the preferableheight. It should be noted, however, that the film thickness of thestrained SiGe layer 31 is determined, to a certain extent, by thecoefficient of straining of the strained SiGe layer 31 asabove-mentioned, and, therefore, it is preferable to control the heighton the NMOS region A side by the film thickness of the insulation layer13, as has been described referring to FIG. 2A above.

Subsequently, the cap film 32 formed of Si, for example, is formed onthe strained SiGe layer 31. In this case, the Si layer is epitaxiallygrown selectively on the strained SiGe layer 31. This ensures that thecap film 32 composed of the Si layer is formed in a strained state.

Next, as shown in FIG. 2J, the SiN film 17 (see FIG. 2I) and the SiO₂film 16 (see FIG. 2I) on the NMOS region A side are removed, to exposethe surface of the strained Si layer 21. In this case, the height of thesurface of the strained Si layer 21 on the NMOS region A side is set tobe roughly equal to the height of the surface of the cap film 32 on thePMOS region B side.

Next, as shown in FIG. 2K, a device isolation region for isolating thedevices is formed between the NMOS region A and the PMOS region B by theordinary STI (Shallow Trench Isolation) technology. Specifically, atrench 14 having such a depth as to reach the inside of the relaxed SiGelayer 12 is formed in the region including the protective film 18 (seeFIG. 2J) between the NMOS region A and the PMOS region B by etchingusing a resist pattern (omitted in the figure) as a mask, and the insideof the trench 14 is filled with a device isolation film 15 formed ofSiO₂, for example.

The steps thereafter are the same as those for an ordinary CMOStransistor. Namely, as shown in FIG. 2L, by a thermal oxidizingtreatment, a gate insulation film (omitted in the figure) composed ofSiO₂ is formed on the surface of the strained Si layer 21 in the NMOSregion A and on the surface of the cap film 32 in the PMOS region B. Inthis case, only the surface side of the cap film 32 may be oxidized, orthe whole region in the film thickness direction of the cap film 32 maybe oxidized. Subsequently, a gate electrode film (omitted in the figure)is formed on the gate insulation film, and the gate electrode film ispatterned, to form gate electrodes 22 and 33 respectively in the NMOSregion A and the PMOS region B.

Next, an n-type impurity composed of arsenic (As⁺), for example, isintroduced into the surface side of the strained Si layer 21 on bothsides of the gate electrode 22 in the NMOS region A, to form LDD regions24. Besides, a p-type impurity composed of boron (B⁺), for example, isintroduced into the surface side of the gate electrode 33 in the PMOSregion B, to form LDD regions 35. Thereafter, an insulation film(omitted in the figure) composed of SiO₂, for example, is formed on thestrained SiGe layer 31 and on the strained Si layer 21 so as to coverthe gate electrodes 22 and 33. Subsequently, the insulation film isetched back (removed) by reactive ion etching, and side walls 23 and 34are formed respectively at side walls of the gate electrodes 22 and 33.

Subsequently, an n-type impurity composed of As⁺ is introduced into thesurface side of the strained Si layer 21 on both sides of the gateelectrode 22 provided with the side wall 23 in the NMOS region A, toform source/drain (SD) regions 25. Besides, a p-type impurity composedof B⁺ is introduced into the surface side of the strained SiGe layer 31on both sides of the gate electrode 33 provided with the side wall 34 inthe PMOS region B, to form SD regions 36. Thereafter, a heat treatmentat 800-1500° C. is conducted in an inert gas atmosphere, whereby theimpurities in the LDD regions 24, 35 and the SD regions 25, 36 arediffused, to achieve activation. As a result, a channel region 26defined between the source/drain regions 25 with the LDD region 24therebetween is formed in the strained Si layer 21 in the NMOS region A,whereas a channel region 37 defined between the SD regions 36 with theLDD region 35 therebetween is formed in the strained SiGe layer 31 inthe PMOS region B.

Thereafter, a high melting point metal film (omitted in the figure)composed of cobalt (Co) or nickel (Ni), for example, is formed on theentire surfaces of the strained SiGe layer 31, the device isolation film15 and the stained Si layer so as to cover the gate electrodes 22 and 33provided with the side walls 23 and 34. Next, a heat treatment isconducted to silicidize the surface side of the gate electrodes 22, 33and the SD regions 25, 36. By this, a semiconductor device havingsilicide layers 27, 38 formed on the surface side of the gate electrode22, 33 and the SD regions 25, 36 can be obtained. Thereafter, theunreacted high melting point metal film is removed.

According to the semiconductor device and the method of manufacturingthe same as above-described, the channel region 26 in the NMOS region Aprovided on the substrate 11 is formed in the strained Si layer in thetension-strained state with the plane orientation (100) optimum forenhancing the electron mobility, and the channel region 37 in the PMOSregion B on the substrate 11 is formed in the strained SiGe layer 31 inthe compression-strained state with the plane orientation (110) optimumfor enhancing the hole mobility. This makes it possible to enhance thecarrier mobility (electron mobility) in the NMOS transistor 20 of theCMOS device and the carrier mobility (hole mobility) in the PMOStransistor 30 of the CMOS device. Therefore, it is possible to enhancethe performance of the CMOS device.

In addition, the heights of the surface layers in the NMOS region A andthe PMOS region B are controlled to be roughly equal to each other,whereby generation of a step between the NMOS region A and the PMOSregion B is restrained; therefore, contact holes for connection to thetransistors formed in the regions can be formed with high accuracy, andthe yield of the CMOS device can be enhanced.

Incidentally, while the NMOS transistor 20 is provided in the strainedSi layer (first semiconductor layer) 21 in this embodiment, the presentinvention is not limited to this configuration, and the firstsemiconductor layer may be a non-strained Si layer. In this case, in thestep described above referring to FIG. 2A, a joined substrate 41composed of an Si layer with a surface plane orientation of (100) islaminated directly on the insulation layer 13 to form an SOI structurefor an NMOS transistor 20, and the NMOS transistor 20 is formed on thejoined substrate 41. By this, the NMOS transistor 20 can be formed inthe first semiconductor layer having a plane orientation (100) whichpromises a highest electron mobility. It should be noted, however, thatit is preferable to form the first semiconductor layer of the strainedSi layer 21, since this configuration promises further enhancement ofthe electron mobility in the NMOS transistor 20.

Besides, while the strained Si layer (first semiconductor layer) 21 withthe plane orientation (100) is used for the NMOS region A and thestrained SiGe layer (second semiconductor layer) 31 with the planeorientation (110) is used for the PMOS region B in this embodiment, thepresent invention is not limited to this configuration, and asemiconductor layer with a plane orientation of (111) may be used aseither one of the first semiconductor layer and the second semiconductorlayer. As has been mentioned in the description of the background art,the electron mobility is higher in the order in terms of planeorientation of (100)>(111)>(110) and the hole mobility is higher in theorder in terms of plane orientation of (110)>(111)>(100); therefore, asemiconductor layer having the plane orientation (111) shows a mediumlevel of electron mobility and a medium level of hole mobility.

By thus using the first semiconductor layer with the plane orientation(111) in the NMOS region A, the electron mobility can be enhanced ascompared with the case of using a semiconductor layer with a planeorientation of (110). In this case, an Si substrate composed of an Sisingle crystal layer with a surface plane orientation of (111) as thejoined substrate 41, a strained Si layer 21 with a plane orientation of(111) is formed in the condition of maintaining the plane orientation,with a relaxed SiGe layer 42 therebetween, and it is laminated on theinsulation layer 13.

In addition, by using the second semiconductor layer with the planeorientation (111) in the PMOS region B, the hole mobility can beenhanced as compared with the case of using a semiconductor layer with aplane orientation of (100). In this case, an Si substrate composed of anSi single crystal layer with a surface lane orientation of (111) as thesubstrate 11, and, in the condition of maintaining this planeorientation, a strained SiGe layer with a plane orientation of (111) isepitaxially grown, with a relaxed SiGe layer 12 therebetween.

It should be noted, however, that it is preferable to use the firstsemiconductor layer with the plane orientation (100) as the NMOS regionA and to use the second semiconductor layer with the plane orientation(110) in the PMOS region B, since the electron mobility and the holemobility can thereby be further enhanced.

Second Embodiment

FIG. 3 shows a sectional configurational diagram of a CMOS transistor inthis embodiment. As shown in the figure, in this embodiment, an examplewill be described in which a p-type Si substrate composed of an Sisingle crystal layer with a surface plane orientation of (100) is usedas the substrate 11 in the first embodiment, and a PMOS region (firstdevice region) B′ and an NMOS region (second device region) A′ areprovided on the substrate 11. Incidentally, the same configurations asin the first embodiment will be denoted by the same symbols as usedabove, in the following description.

As shown in the figure, a relaxed SiGe layer 12 is provided on thesubstrate 11 in the state of maintaining the plane orientation (100) ofthe surface of the substrate 11. Though omitted in the figure, therelaxed SiGe layer 12 is composed, for example, of an inclined SiGelayer containing Ge mixed in an Si layer so that the compositional ratioof Ge in the Si layer gradually increases from 0 to x in the directiontoward the upper layer, and an Si_(1-x)Ge_(x) layer which is provided onthe inclined SiGe layer and in which the compositional ratio of Ge inthe Si layer is x.

Here, the coefficient of straining of a strained Si layer 21 provided onthe relaxed SiGe layer 12 is determined by the compositional ratio of Siand Ge in the Si_(1-x)Ge_(x) layer of the relaxed SiGe layer 12, and,therefore, the compositional ratio in the Si_(1-x)Ge_(x) layer of therelaxed SiGe layer 12 is so controlled as to provide the strained Silayer 21 with a coefficient of straining which is optimum for enhancingthe electron mobility.

In addition, an insulation layer 13 composed of SiO2 is provided on therelaxed SiGe layer 12 in the PMOS region B′, and a strained SiGe layer(first semiconductor layer) 31 in a compression-strained state isprovided on the insulation layer 13. The strained SiGe layer 31 isformed to have a plane orientation of (110) which is different from theplane orientation (100) of the substrate 11 and which can enhance thehole mobility as compared with other plane orientations. Besides, thestrained SiGe layer 31, by being in the compression-strained state, isconfigured to promise a higher hole mobility as compared with anon-strained Si layer.

As will be detailed in the manufacturing method which will be describedlater, the strained SiGe layer 31 is formed from, and in the state ofmaintaining the plane orientation of, a p-type Si substrate (joinedsubstrate) composed of an Si single crystal layer whose surface has aplane orientation of (110), different from that of the substrate 11. ThePMOS region B′ is configured in the condition where the strained SiGelayer 31 is laminated on the insulation layer 13. In addition, a thinfilm form cap film 32 formed of Si, for example, is provided on thestrained SiGe layer 31.

On the other hand, on the relaxed SiGe layer 12 in the NMOS region A′ isprovided a strained Si layer (second semiconductor layer) 21 in atension-strained state. The strained Si layer 21, by being in thetension-strained state, is configured to have a higher electron mobilityas compared with a non-strained layer. In addition, the strained Silayer 21 is provided in the state of maintaining the plane orientationof the relaxed SiGe layer 12, i.e., in the state of maintaining theplane orientation (100) of the surface of the substrate 11, so that ithas the plane orientation of (100) which enhances the electron mobilityas compared with other plane orientations. Incidentally, while thestrained Si layer 21 in the tension-strained state is provided here, thestrained layer is not particularly limited inasmuch as it is a strainedlayer in a tension-strained state which can enhance the electronmobility.

A trench 14 in the state of reaching the inside of the relaxed SiGelayer 12 is provided on the surface side between the NMOS region A′ andthe PMOS region B′, and a device isolation film 15 composed of SiO₂ isprovided in the trench 14. The NMOS region A′ and the PMOS region B′isolated by the device isolation film 15 are provided respectively withan NMOS transistor 20 and a PMOS transistor 30. These transistors areconfigured in the same manner as in the first embodiment.

Namely, the NMOS transistor 20 has a gate electrode 22 provided on theupper side of the strained Si layer 21, with a gate insulation film(omitted in the figure) therebetween, and side walls 23 are provided onboth sides of the gate electrode 22. In addition, SD regions 25 areformed in the strained Si layer 21 on both sides of the gate electrode22, with an LDD region 24 therebetween. Then, that region of thestrained Si layer 21 which is defined between the SD regions (N⁺ typediffusion regions) 25, with the LDD region 24 therebetween, constitutesa channel region 26. Besides, a silicide layer 27 is provided on thesurface side of the gate electrode 22 and the SD regions 25.

On the other hand, the PMOS transistor 30 has a gate electrode 33 formedon the upper side of the strained SiGe layer 31, with a gate insulationfilm (cap film 32) therebetween, and side walls 34 are provided on bothsides of the gate electrode 33. In addition, SD regions (P⁺ typediffusion regions) 36 are formed in the strained SiGe layer 31 on bothsides of the gate electrode 33, with an LDD region 35 therebetween.Then, that region of the strained SiGe layer 31 which is defined betweenthe SD regions 36, with the LDD region 35 therebetween, constitutes achannel region 37. Besides, a silicide layer 38 is provided on thesurface side of the gate electrode 33 and the SD regions 36.

Now, a method of manufacturing the above-described CMOS device isillustrated in manufacturing step sectional diagrams in FIGS. 4A to 4L.

As shown in FIG. 4A, a substrate 11 composed of a p-type Si substrateobtained by growing an Si single crystal layer whose surface has a planeorientation of (100), for example, is provided with an NMOS region (NMOSforming region) A′ for forming an NMOS transistor in a latter step and aPMOS region (PMOS forming region) B′ for forming a PMOS transistor in alatter step. Here, the NMOS region A′ corresponds to the second deviceregion in the claims, and the PMOS region B′ to the first device region.

First, a relaxed SiGe layer 12 is epitaxially grown on the substrate 11in the state of maintaining the plane orientation (100) of the substrate11. In this case, an inclined SiGe layer with the compositional ratio ofGe to Si gradually increasing from 0 to x in the direction toward theupper layer is epitaxially grown, and thereafter an Si_(1-x)Ge_(x) layerwith the compositional ratio of Si and Ge being 1-x:x is epitaxiallygrown on the inclined SiGe layer, to form the relaxed SiGe layer 12composed of the inclined SiGe layer and the Si_(1-x)Ge_(x) layer.

Here, the coefficient of straining of a strained Si layer to be formedon the relaxed SiGe layer 12 in a latter step is determined by thecompositional ratios of Si and Ge in the relaxed SiGe layer and theSi_(1-x)Ge_(x) layer, and the strained Si layer is to be provided with achannel region for an NMOS transistor; therefore, the compositionalratios in the relaxed SiGe layer 12 and the Si_(1-x)Ge_(x) layer are soset as to provide a coefficient of straining which is optimum forenhancing the electron mobility.

Next, an insulation layer 13 composed of SiO₂, for example, is formed onthe relaxed SiGe layer 12. Here, by regulating the film thickness of theinsulation layer 13, the height of the surface of a PMOS region B′provided by forming a strained SiGe layer and a cap film on theinsulation layer 13 is controlled. This ensures that in the subsequentstep in which the strained SiGe layer and the insulation layer 13 on theNMOS region A′ side are removed to expose the relaxed SiGe layer 12 andthen a strained Si layer is grown on the relaxed SiGe layer 12 to form asurface layer of the NMOS region A′, the heights of the surfaces of theNMOS region A′ and the PMOS region B′ are controlled to be roughly equalto each other.

On the other hand, a relaxed SiGe layer 42 is epitaxially grown on ajoined substrate 41 composed of a p-type Si substrate having a surfaceplane orientation of (110) different from the plane orientation (100) ofthe surface of the substrate 11, in the state of maintaining the planeorientation (110) of the joined substrate 41. In this case, an inclinedSiGe layer in which the compositional ratio of Ge to Si graduallyincreases from 0 to z in the direction toward the upper layer isepitaxially grown, and thereafter an Si_(1-z)Ge_(z) layer with acompositional ratio of Si and Ge being 1-z:z is epitaxially grown on theinclined SiGe layer, thereby forming the relaxed SiGe layer 42 composedof the inclined SiGe layer and the Si_(1-z)Ge_(z) layer.

Here, the coefficient of straining of a strained SiGe layer to be formedon the relaxed SiGe layer 42 in the subsequent step is determined by thecompositional ratio of Si and Ge in the Si_(1-z)Ge_(z) layer of therelaxed SiGe layer 42 and the compositional ratio of Si and Ge in thestrained SiGe layer, and a channel region for a PMOS transistor isformed in the strained SiGe layer; therefore, the compositional ratio inthe Si_(1-z)Ge_(z) layer is so set as to provide a coefficient ofstraining which is optimum for enhancing the hole mobility.

Subsequently, the strained SiGe layer (first semiconductor layer) 31 ina compression-strained state is epitaxially grown on the relaxed SiGelayer 42. The strained SiGe layer 31 in the compression-strained stateis formed of an Si_(1-y)Ge_(y) (z<y) having a Ge compositional ratiohigher than that of the Si_(1-z)Ge_(z) layer on the upper layer sideconstituting the relaxed SiGe layer 42. A channel region for a PMOStransistor is to be formed in the strained SiGe layer 31 in a latterstep, and, therefore, the compositional ratio of Si and Ge in theSi_(1-y)Ge_(y) layer is so set as to provide a coefficient of strainingwhich is optimum for enhancing the hole mobility. Here, the height ofthe surface of the PMOS region B can be controlled also by the filmthickness of the strained SiGe layer 31. However, since the filmthickness of the strained SiGe layer 31 is determined, to a certainextent, according to the coefficient of straining, it is preferable tocontrol the height of the surface of the PMOS region B′ by the filmthickness of the insulation layer 13, as has been mentioned above.

Next, the insulation layer 13 formed side of the substrate 11 and thestrained SiGe layer 31 formed side of the joined substrate 41 areopposed to each other, and the insulation layer 13 and the strained SiGelayer 31 are laminated on each other. As a result, the strained SiGelayer 31 having a plane orientation (110) different from the planeorientation of the substrate 11 is formed on the substrate 11.

Thereafter, as shown in FIG. 4B, hydrogen is introduced into the joinedsubstrate 41 (see FIG. 4A) and the relaxed SiGe layer 42 (see FIG. 4A),and the joined substrate 41 and the relaxed SiGe layer 42 are removed byetching, whereby the substrate 11 is brought into the condition wherethe strained SiGe layer 31 is provided on the insulation layer 13.

Next, as shown in FIG. 4C, an SiO₂ film 16 is formed on the strainedSiGe layer 31, and then an SiN film 17 is formed on the SiO₂ film 16.Subsequently, as shown in FIG. 4D, a resist pattern R is formed in thecondition where the SiN film 17 on the NMOS region A′ side is exposed.Next, as shown in FIG. 4E, by etching using the resist pattern R (seeFIG. 4D) as a mask, the SiN film 17 and the SiO₂ film 16 are removed.Thereafter, the resist pattern R is removed.

Subsequently, as shown in FIG. 4F, the strained SiGe layer 31 and theinsulation layer 13 on the NMOS region A′ side are removed by etchingusing the SiN film 17 and the SiO₂ film 16 as a mask, whereby thesurface of the relaxed SiGe layer 12 is exposed.

Next, as shown in FIG. 4G, a protective film 18 composed of SiN isformed on the relaxed SiGe layer 12, in the state of covering the SiNfilm 17, the SiO₂ film 16, the strained SiGe layer 31 and the insulationlayer 13 on the PMOS region B′ side. Thereafter, as shown in FIG. 4H,the protective film 18 is etched back, whereby the protective film 18 isleft in the state of covering the side walls of the insulation layer 13,the strained SiGe layer 31, the SiO₂ film 16 and the SiN film 17 on therelaxed SiGe layer 12 on the PMOS region B′ side, and the surface of therelaxed SiGe layer 12 on the NMOS region A′ side is exposed. Theprotective film 18 is provided for preventing an Si layer from growingsideways from the strained SiGe layer 31 on the PMOS region B′ side atthe time of epitaxially growing a strained Si layer on the relaxed SiGelayer 12 on the NMOS region A′ side in the subsequent step.

Subsequently, as shown in FIG. 4I, the strained Si layer 21 in atension-strained state is epitaxially grown on the relaxed SiGe layer12. In this case, it is preferable to grow the strained Si layer 21 to aheight roughly equal to the height of the strained SiGe layer 31 on thePMOS region B′ side. It should be noted, however, that since the filmthickness of the strained Si layer 21 is determined to a certain extentaccording to the coefficient of straining of the strained Si layer 21 asabove-mentioned, it is preferable to control the height of the surfaceon the PMOS region B′ side by the film thickness of the insulation layer13, as has been described above referring to FIG. 4A.

Next, as shown in FIG. 4J, the SiN film 17 (see FIG. 4I) and the SiO₂film 16 (see FIG. 4I) on the PMOS region B′ side are removed, wherebythe surface of the strained SiGe layer 31 is exposed. Thereafter, a capfilm 32 formed of Si, for example, is formed on the strained SiGe layer31. In this case, the Si layer is epitaxially grown on the strained SiGelayer 31. By this, the cap film 32 composed of the Si layer is formed ina strained state. Besides, since the surface of the strained Si layer 21is also exposed, the condition where the Si layer is further grown onthe strained Si layer 21 is obtained.

Incidentally, while the cap film 32 is formed by exposing the surface ofthe strained SiGe layer 31 after the growth of the strained Si layer 21here, a process may be adopted in which in the step described abovereferring to FIG. 4B, the strained SiGe layer 31 is formed on theinsulation layer 13, and thereafter the Si layer is epitaxially grown onthe surface of the strained SiGe layer 31 to thereby form the cap film32. In this case, the cap film 32 in the NMOS region A′ is removedtogether when the insulation layer 13 and the strained SiGe layer 31 onthe NMOS region A′ side are removed in the latter step described abovereferring to FIG. 4F.

Subsequently, as shown in FIG. 4K, by etching using a resist pattern asa mask, a trench 14 with such a depth as to reach the inside of therelaxed SiGe layer 12 is formed in the region including the protectivefilm 18 (see FIG. 4J) between the NMOS region A′ and the PMOS region B′,and the inside of the trench 14 is filled with a device isolation film15 composed of SiO₂, for example.

The subsequent steps are carried out by steps similar to those for anordinary CMOS transistor, in the same manner as in the first embodiment,whereby an NMOS transistor 20 is formed in the NMOS region A′ and a PMOStransistor 30 is formed in the PMOS region B′, as shown in FIG. 4L.

Even in the semiconductor device and the method of manufacturing thesame as above-described, the NMOS transistor 20 is formed in thestrained Si layer 21 in the tension-strained state having the planeorientation (100) optimum for enhancing the electron mobility, in theNMOS region A′, and the PMOS transistor 30 is formed in the strainedSiGe layer 31 in the compression-strained state having the planeorientation (110) optimum for enhancing the hole mobility. This makes itpossible to enhance the electron mobility in the NMOS transistor 20 andthe hole mobility in the PMOS transistor 30, in the CMOS device.Therefore, it is possible to enhance the performance of the CMOS device.

In addition, since the generation of a step between the NMOS region A′and the PMOS region B′ is restrained by controlling the heights of thesurfaces of the NMOS region A′ and the PMOS region B′ to be roughlyequal to each other, contact holes for connection to transistors formedin the regions can be formed with high accuracy, and the yield of theCMOS device can be enhanced.

Incidentally, while the PMOS transistor 30 is provided in the strainedSiGe layer 31 in this embodiment, the present invention is not limitedto this configuration, and the PMOS transistor 30 may be formed in anon-strained Si layer. In this case, in the step described abovereferring to FIG. 4A, a joined substrate 41 composed of an Si layerwhose surface has a plane orientation of (110) is laminated directly onthe insulation layer 13. Then, the PMOS transistor 30 is formed on thejoined substrate 41. By this, the PMOS transistor 30 can be formed inthe first semiconductor layer having a plane orientation (110) optimumfor enhancing the hole mobility. It should be noted, however, that it ispreferable to form the PMOS transistor 30 in the strained SiGe layer 31in the compression-strained state, since the hole mobility in the PMOStransistor 30 can thereby be further enhanced.

Besides, while the strained SiGe layer (first semiconductor layer) 31with the plane orientation (110) is used for the PMOS region (firstdevice region) B′ and the strained Si layer (second semiconductor layer)21 with the plane orientation (100) is used for the NMOS region (seconddevice region) A′ in this embodiment, the present invention is notlimited to this configuration; a semiconductor layer with a planeorientation of (111) may be used as either one of the firstsemiconductor layer and the second semiconductor layer, in the samemanner as in the first embodiment.

By using the second semiconductor layer with the plane orientation (111)in the NMOS region A′, the electron mobility can be enhanced, ascompared with the case of using the semiconductor layer with the planeorientation (110). In this case, an Si substrate comosed of an Si singlecrystal layer whose surface has a plane orientation of (111) is used asthe substrate 11, and, in the condition of maintaining this planeorientation, the strained Si layer 21 with the plane orientation (111)is epitaxially grown, with the relaxed SiGe layer 12 therebetween.

Besides, by using the first semiconductor layer with the planeorientation (111) in the PMOS region B′, the hole mobility can beenhanced, as compared with the case of using the semiconductor layerwith the plane orientation (110). In this case, an Si substrate composedof an Si single crystal layer whose surface has a plane orientation of(111) is used as the joined substrate 41, and, in the condition ofmaintaining this plane orientation, the strained SiGe layer 31 with theplane orientation (111) is formed thereon, with the relaxed SiGe layer42 therebetween, and it is laminated on the insulation layer 13.

It should be noted, however, that it is preferable to use the secondsemiconductor layer with the plane orientation (100) in the NMOS regionA′ and to use the first semiconductor layer with the plane orientation(110) in the PMOS region B′, since the electron mobility and the holemobility can thereby be further enhanced.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alterations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalents thereof.

1. A semiconductor device comprising: a substrate; a first device regionand a second device region in the substrate; a gate electrode associatedwith each device region: a first semiconductor layer on said substratein said first device region and having a plane orientation differentfrom that of the surface of said substrate; a second semiconductor layeron said substrate in said second semiconductor region and comprised of astrained layer having the same plane orientation as that of the surfaceof said substrate; a thin film cap on the second semiconductor layereffective to enhance the interface between the second semiconductorlayer and the gate electrode, wherein, said first and secondsemiconductor layers do not overlap within said first and second deviceregions.
 2. The semiconductor device as set forth in claim 1, wherein:said first device region is an NMOS transistor region; said seconddevice region is a PMOS transistor region; the plane orientation of saidfirst semiconductor layer is (100); and said second semiconductor layeris comprised of a strained layer in a compression-strained state.
 3. Thesemiconductor device as set forth in claim 1, wherein: said first deviceregion is a PMOS transistor region; said second device region is an NMOStransistor region; the plane orientation of said first semiconductorlayer is (110); and said second semiconductor layer is comprised of astrained layer in a tension-strained state.
 4. The semiconductor deviceas set forth in claim 1, wherein said first semiconductor layer isformed of a strained layer.
 5. The semiconductor device as set forth inclaim 4, wherein: said first device region is an NMOS transistor region;said second device region is a PMOS transistor region; said firstsemiconductor layer is comprised of a strained layer in atension-strained state with a plane orientation of (100); and saidsecond semiconductor layer is comprised of a strained layer in acompression-strained state with a plane orientation of (110).
 6. Thesemiconductor device as set forth in claim 4, wherein: said first deviceregion is a PMOS transistor region; said second device region is an NMOStransistor region; said first semiconductor layer is comprised of astrained layer in a compression-strained state with a plane orientationof (110); and said second semiconductor layer is comprised of a strainedlayer in a tension-strained state with a plane orientation of (100). 7.The semiconductor device as set forth in claim 1, wherein: said firstsemiconductor layer is laminated on said substrate with an insulationlayer therebetween; and said second semiconductor layer is formed onsaid substrate by epitaxial growth.